Microwaving a ready meal in its plastic tray can release thousands of microscopic plastic particles into the food within minutes, even when the packaging is labelled 'microwave-safe', according to a new analysis published by Greenpeace International on Tuesday.
The analysis, based on peer-reviewed studies, found that heat triggers the release of microplastics and nanoplastics, as well as chemicals like bisphenols and phthalates, which are linked to hormone disruption, infertility and certain cancers. One study cited found that between 326,000 and 534,000 particles leached into food simulants after five minutes of microwaving, up to seven times more than oven heating under similar conditions.
Heating plastics like polypropylene and polystyrene increased the migration of additives such as plasticisers and antioxidants into food. 'People think they're making a harmless choice when they buy and heat a meal packaged in plastic,' said Graham Forbes of Greenpeace USA. 'In reality, we are being exposed to a cocktail of microplastics and hazardous chemicals.'
The report notes that 'microwave-safe' labels only indicate a container will not visibly melt or break, not that it prevents particle release. Over 4,200 hazardous chemicals are used in plastics, with many not regulated in food packaging. The analysis also found that worn or scratched containers released nearly double the particles, and that refrigeration for over six months can also release particles.
Plastic-packaged ready meals are a fast-growing sector worth nearly $190bn, with global production reaching 71 million tonnes in 2024. Greenpeace argues regulation has not kept pace with research, and labels like 'microwave safe' give a false sense of safety.
